Each year, businesses incur considerable expenses from goods that are damaged during transportation on trucks, trains, and other carriers. The problem is especially severe for fragile goods such as plants, which are usually shipped in loose arrangement on shelving units. Thus, nurseries, for example, lose a significant portion of their profit margin to plants that are mutilated or destroyed during transportation from the nursery to the customer.
Much of the damage to goods that occurs during transportation on a carrier arises from spillage or movement of the goods when the carrier makes turns. Even at modest speeds, the centrifugal forces acting on items stacked on a shelving unit forces the items away from the center of the carrier bed when the carrier makes a turn, resulting in shifting and spillage of the goods if they are not adequately secured.
A number of attempts have been made to develop shelving assemblies that will prevent spillage of goods stacked upon them. For example, U.S. Pat. No. 5,037,256 (Schroeder) discloses a dunnage bar lock arrangement supported on vertical struts. The arrangement is useful for the shipment of paneled goods, such as automobile doors. The paneled goods are supported on parallel horizontal bars, and are kept separate by dividers that are supported on a central horizontal bar. The usefulness of this device is limited to paneled goods.
Shelving assemblies have been developed that are supported on posts that interface with rectangular apertures set into the bed or sides of a carrier. U.S. Pat. No. 5,108,141 (Anderson), for example, discloses a rack for a truck canopy. The rack consists of a series of vertical and horizontal struts, which interconnect into a framework. The vertical struts of the framework are supported on bases, which fit into holes with rectangular braces provided along the top of the walls of the truck bed.
Alternatively, shelving assemblies may be equipped with hollow rectangular shoes that interface with similarly shaped posts or protrusions provided along the bed of a carrier. Thus, U.S. Pat. No. 4,565,402 (Hopkins) discloses units of a support frame for a truck bed. The units are hollow rectangular posts that receive rectangular struts. U.S. Pat. No. 3,830,380 (Spencer) discloses a multi-level container for carrying construction materials and includes a series of vertically stackable shelving assembly. The vertical struts of the shelving assembly have hollow rectangular shoes that fit over the rectangular posts of a base frame secured to the bed of a truck.
Shelving assemblies provided with rectangular shoe and post assemblies have the advantage that they resist rotational movement of the assembly and prevent it from tipping over, thereby ensuring that the shelving assembly remains securely attached to the carrier bed. However, this type of shoe and post assembly does not reduce the centrifugal force on items which are stacked upon the shelving units, and thus does not reduce shifting and spillage of those items. Furthermore, this type of shoe and post assembly requires precise alignment of the shoes and posts when the shelving assembly is assembled or mounted on a carrier bed. This results in significant difficulties if the shelving assembly is not manufactured with precise uniformity or if the dimensions of the assembly change slightly with age or use. Furthermore, the posts can only be disengaged from the shoes by lifting the shelving units in a direction perpendicular to the base of the shoe, which is undesirable when the shelving units are heavy or are loaded with merchandise. Also, because of the large surface area of contact between the shoes and the posts, there is a pronounced tendency for the posts to stick to the sides of the shoes if they are left engaged for an extended period of time.
Some shelving assemblies have rounded support posts that engage rounded shoes. U.S. Pat. No. 3,118,249 (Bard et al.) discloses a shelving assembly for mushrooms in which the individual shelving units are vertically stacked so that the rounded support posts of each unit engages the rounded shoes of the neighboring unit. Danish patent 93547 discloses a similar shelving unit, except that the rounded shoes are tapered outwardly from the interior of the shoe.
While the rounded shoe and post assemblies disclosed in these references solve some of the problems associated with rectangular shoe and post assemblies, they are still unsatisfactory in some respects. For example, the shoes of the shelving assembly disclosed in U.S. Pat. No. 3,118,249 have wide rims which meet the rounded portion at a sharp angle, as illustrated in FIG. 7 of that reference. As with rectangular shoe and post assemblies, this requires precise alignment of the shoe with the post when the shelving assemblies are being put together, a feature which, as noted before, is undesirable when the shelving units are heavy or are loaded with merchandise. More importantly, however, the engaging power of the shoe to the post is compromised by this design as compared to the design involving rectangular posts and receptacles, since the rounded surface of the post provides significantly less resistance to tilting of the shelving assembly when torque is applied to the post. Thus, shelving units incorporating this type of shoe and post assembly tend to tip over easily or to disengage from neighboring units when the shelving assembly as a whole is jolted. The problem is even more severe for shelving assemblies of the type disclosed in Danish patent 93547 since the shoes in those assemblies are tapered outwardly, thus providing even less resistance to disengagement. Thus, while shelving assemblies of that type are suitable for their intended purpose (i.e., as cheese shelves in a cheese warehouse), they are unsuitable for use in transporting and displaying goods on a carrier.
In an attempt to reduce movement or spillage of goods stacked on shelving units on a carrier, a number of shelving assemblies have been developed which are tilted inwardly toward the center of the truck bed. The tilting of the shelving assembly reduces the tendency for items stacked on the shelving units to shift or spill in response to centrifugal forces. Thus, for example, U.S. Pat. No. 3,893,705 (Allen) relates to a system for transporting sheets of glass on a truck. According to the system, sheets of glass are mounted on vertical shelving units consisting of separate support frames that tilt inwardly towards each other. The shelving units are supported on wheels which fit into grooves set in the truck bed. U.S. Pat. No. 3,057,489 (Gilliam) relates to a truck body for carrying bottle cases in a shelving assembly. The truck body is equipped in the center with a flange that terminates in roller bearings and is supported on a hydraulic lift. The sides of the truck are fitted with hinges. The shelving assembly is supported on one side by the hinges and on the other side by the roller bearings. In use, the hydraulic lift is lowered after the bottle cases have been loaded so that the shelving assembly tilts inwardly toward the center of the truck bed. U.S. Pat. No. Re. 23,848 (Gerhardt) discloses a shelving assembly for transporting stacked articles. The assembly consists of opposite rows of shelving units which are hinged to the side of the truck and which tilt inwardly toward the center of the truck bed. The shelving assembly is secured along the center of the truck bed by a z-shaped shoe.
While these shelving assemblies are designed to prevent shifting or spillage of items stacked on them, they suffer from many infirmities which make them unsuitable for the present purposes. The device of U.S. Pat. No. 3,893,705 (Allen), for example, is suitable only for use with paneled goods, such as sheets of glass, while U.S. Pat. No. 3,057,489 (Gilliam) and U.S. Pat. No. Re. 23,848 (Gerhardt) require specially designed truck beds.
Applicant's shelving assembly proposed in U.S. Pat. No. 5,233,931 (McCorkle) is useful for transporting plants and other fragile goods and addresses many of the infirmities of the prior art. The shelving units of that assembly are provided with semi-spherical shoes. The present invention, which represents a further improvement of the design of that rack, provides greater resistance to tilting of the shelving assembly, while at the same time being easier to mount and dismount than shelving units equipped with rectangular shoe and post assemblies. The shelving assemblies of the present invention also provide greater resistance to spillage or movement of goods stacked on the shelving assembly during transportation on a carrier.